The present invention relates to an excitation system for exciting a semiconductor laser device, and more particularly to an excitation system for exciting a semiconductor laser device used in a laser printer.
One conventional modulation system includes a light source for generating a laser beam, an acoustooptic effect device, and a pinhole, in which the laser beam generated from the light source is polarized by the acoustooptic effect device and the resultant laser beam is subjected to modulation while passing it through the pinhole. Another conventional modulation system includes a semiconductor laser device, an auto power controller (APC), and a switching circuit for controlling flickering of the semiconductor laser to thus carries out a pulse width modulation.
However, the former modulation system is involved with problems such that the overall system is enlarged due to the provision of the acoustooptic effect device and the pinhole, and the system is liable to be affected by vibrations. The latter modulation system is also involved with problems such that the modulation cannot be performed with a high frequency because the modulating operation is performed in a discrete fashion.
In view of the problems involved with the conventional systems, researches and developments have recently be focused on the use of a semiconductor laser device with which an excitation signal of the semiconductor laser device is modulated to directly perform an amplitude modulation. This method, however, is not practically available due to the fact that properties of the semiconductor laser device change depending upon external factors, such as ambient temperature, and thus the modulation cannot be stably achieved.